The terms mitochondrial myopathy, mitochondrial cytopathy and inherited mitochondrial encephalomyopathy encompass a large grouping of syndromes produced either by genetically transmitted or acquired disruption of mitochondrial energy production or biosensor function. Many of these disorders are clinically apparent during infancy, but for some the metabolic signs of oxidative stress may not appear until the young or middle adult years. Initially thought to be a rare disorder, it now appears that mitochondrial dysfunction is relatively common but often unrecognized because symptoms are extremely variable and usually insidious in onset. It has also become apparent that mitochondrial dysfunction is a component of many common cardiovascular and neurological disease states and of physiologic aging. Recent advances in our understanding of the mechanisms of mitochondrial dysfunction may explain and link a wide variety of clinical phenomena. This review summarizes the current knowledge regarding the clinical implications of inherited and acquired mitochondrial disease, the effects of anesthetics on mitochondrial function, and the extent to which mitochondrial bioenergetic state determines anesthetic requirement and potential anesthetic toxicity.